This invention relates to an electrically controlled brake assembly for a vehicle wheel and, more particularly, to a brake assembly of the type in which an operating arm is mounted between its ends to turn back and forth about a pivot on a backing plate and carries at least one electromagnet on one of its ends. When energized, the electromagnet frictionally engages an armature which rotates with and usually forms part of the drum of the vehicle wheel structure. Such frictional engagement causes the operating arm to turn about the pivot in one direction or the other depending upon the direction of rotation of the drum. The end of the operating arm opposite the electromagnet is disposed between a pair of pivoted brake shoes and, depending upon the direction in which the arm is turned, such end bears against one or the other of the shoes to force the shoes outwardly into braking engagement with the drum.
The forces exerted on the two ends of the operating arm during braking are such as to apply a twisting couple to the arm and tend to cock the arm on its pivot. Various arrangements have been proposed to restrict such cocking in order to avoid damaging the operating arm and/or the pivot and to keep the face of the magnet parallel with the face of the armature. Typical examples of such arrangements are disclosed in Birge U.S. Pat. No. 3,134,463 and Marti U.S. Pat. No. 3,788,432. SUMMARY OF THE INVENTION
The general aim of the present invention is to provide a comparatively simple guide which is located directly adjacent the electromagnet and which coacts with the operating arm in a unique manner to restrict twisting and cocking of the arm, the location of the guide adjacent the magnet serving to more effectively resist such cocking and to more effectively maintain the magnet in parallel relation with the armature.
A more detailed object is to provide the operating arm with spaced projections located on circumferentially opposite sides of the magnet and adapted to coact with the guide and the backing plate to restrict cocking of the arm in both directions of turning and throughout the entire stroke of the arm.
The invention also resides in the relatively simple and inexpensive construction of the guide and the coacting projections.
These and other objects and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings.